The biotechnological production of biologically active proteins is essential for the development of novel therapeutic and diagnostic tools and procedures. The majority of these synthetically produced peptides is at present obtained from animal cell cultures. In spite of rapidly accumulating knowledge in this field, some aspects of the in vitro production systems such as, for example, cell proliferation and cell death, are still not entirely controllable.
Industrial processes employing animal cells, particularly permanent animal cell lines, require cell numbers in the order of 108 to 1012 cells. According to GMP (good manufacturing practice), the production of a new lot of product has to be started by thawing a frozen cell stock from the master cell bank. The overall efficiency of the culturing and manufacturing process largely depends on the time period necessary for the first cycles of multiplication of the cells starting from a small frozen inoculum.
Speeding up the growth of the cell population can be achieved by supplementing the culture media with nutritional supplements or growth factors. For instance, it is known in the art to use glutamine dipeptide in replacement of monomeric glutamine, because the dimeric form of glutamine is more stable under cell culture conditions. Either way, however, glutamine as a monomer and as a dipeptide serves as a nutrient and is resorbed and metabolized by the cells of the cell culture.
Growth factors may be, for instance, components of animal sera. Their main disadvantage is that they are usually not well defined. Moreover, the use of components of direct animal origin is presently discouraged in pharmaceutical industry due to the danger of transferring viruses, prions or other possibly pathogenic agents from the animal body to the desired end product, e.g., the bioactive proteins. Alternatively, recombinant growth factors, such as insulin or members of the interleukin family, may serve as suitable growth stimulants. Another possibility is to use safe, chemically defined culture media free of any protein component. However, as a rule the generation time in protein-free media is longer than in media supplemented with serum.
Therefore, there is a great demand for techniques capable to intensify and accelerate the growth and/or product yield of cultured animal cells as well as the cell viability during incubation, particularly for industrial scale manufacturing processes. The present invention will contribute to satisfying this demand.